Expansible frame structure



Sept. 19, 1961 J. H. SCHULZE ETAL 3,000,386

EXPANSIBLE FRAME STRUCTURE Filed Dec. 3, 1958 5 Sheets-Sheet 1 BY 4/ a i7 ATTORN YS Sept. 19, 1961 J. H. SCHULZE ETAL 3,000,386

EXPANSIBLE FRAME STRUCTURE Filed Dec. 5, 1958 5 Sheets-Sheet 2 o F o 9 I/Z/' I21? 0 O L O o T o 0 Q 0 o o O o o o o o o 7% 9 INVENTORS (70/222HSc/mlge Stanley c/ifiye Sept. 19, 1961 J. H. SCHULZE ETAL EXPANSIBLEFRAME STRUCTURE 5 Sheets-Sheet 5 Filed Dec. 3, 1958 5 5 my m fidwwm m M5 M A m, a ws W p 1961 J. H. SCHULZE ET AL 3,000,386

E AAAAAAAAAAAAAAAAAAAAA RE Stanley cIBj/e BY W/ Sept. 19, 1961 J. H.SCHULZE ET AL 3,000,386

EXPANSIBLE FRAME STRUCTURE Filed Dec. 5, 1958 5 Sheets-Sheet 5 g'INVENTORS cfafiizfiSclzul e 34 Stanley cl Eye United States Patent G3,000,386 EXPANSIBLE FRAME STRUCTURE John H. Schulze and Stanley J. Bye,Iowa City, Iowa, as-

signors to the State of Iowa, for the use and benefit of the StateUniversity of Iowa, Iowa City, Iowa, an educational institution of IowaFiled Dec. 3, 1958, Ser. No. 778,012

7 Claims. (Cl. 135-4) This invention relates to expansible framestructures, and more particularly to such structures adapted when intheir expanded positions to approximate a curved surface of revolutiongenerated about a vertical axis.

A primary object of the invention is to provide a collapsible framestructure of relatively light weight and compact shape when in itscollapsed position which may be rapidly expanded to define a rigidhollow dome-like structure.

Another object of the invention is to provide an expansible framestructure assembled from relatively light Weight flexible stripsinterconnected to form a dome-like structure of substantial rigidity inits expanded position.

Still another object of'the invention is to provide an expansible framestructure collapsible into a substantially tubular form and expansibleto define aflhollow domelike frame.

In the achievement of the foregoing and other objects, a frame structureembodying the present invention is constructed from a plurality of flatflexible light weight metallic strips. The strips are located with theirlower ends on a base circle which is centered upon a vertical axis ofsymmetry of the structure in either its expanded or collapsed form. Oneseries of strips extends upwardly and circumferentially of the axis inone direction .to have their upper ends located on an apex circle whichis likewise centered upon the axis of symmetry. Each strip in a secondgroup of strips is pivotally connected at its lower end to one of thestrips in the first series of strips and extends upwardly andcircumferentially of the axis in an opposite circumferential directionto the apex circle. At the apex circle each strip of the second group ispivotally connected to a strip of the first group. Between its upper andlower ends, each second strip passes across one or more first strips andis pivotally connected to each first strip. The points of pivotalinterconnection between the ends of the strips are located so that whenthe structure is expanded the strips are flexed into a curvedconfiguration. When the expanded structure defines a hemispherical dome,all strips extend along great circle arcs of the hemispherical dome.

The upper ends of the strips may be coupled by a suitable locking meansto lock the structure in its expanded position'or in 'a positionintermediate the collapsed and fully expanded position. A series oflinks pivotally interconnecting the strips is located to extendcircumferentially around the expanded structure along a circleintermediate the base and apex circles. When in the expanded position,the links definea compression ring serving to hold the structure in thedesired form.

Other objects and advantages of the invention will become apparent byreference to the following specification taken in conjunction with theaccompanyingdrawings.

In the drawings:

FIG. 1 is a schematic diagram in plan elevation of a frame structureembodying the invention;

FIG. 2 is a schematic diagram representing a sectional view of thediagram of FIG. '1 taken on line 22 of FIG. 1;

FIG. 3 is a perspective view of a structure embodying the invention in afully expanded condition;

Patented Sept. 19, 1961 in a partially collapsed condition;

a hemispherical dome-shape.

FIG. 5 is a side view of the structure of FIG. 3 in a nearly fullycollapsed condition;

FIG. 6 is a detail view of a portion of the structure of FIG. 3;

FIG. 7 is a cross-sectional view taken on line 7-7 of FIG. 6;

FIG. 8 is a cross-sectional view taken on the line 8-8 of FIG. 6;

FIG. 9 is a partial plan view of a modified form of structure in a fullyexpanded condition;

FIG. 10 is a cross-sectional view of the structure of FIG. 9 taken online 1010 of FIG. 9;

FIG. 11 is a view similar to FIG. 10 showing the structure in apartially collapsed condition; FIG. 12 is a detail view of a modifiedform of structure with certain parts broken away and others shown insection showing the parts in a partially collapsed condition;

FIG. 13 is a view similar to FIG. 12 showing the structure of FIG. 12 ina fully expanded condition; and FIG. 14 is a detail cross-sectional viewtaken on line 14-14 of FIG. 13.

The frame structure disclosed in the drawings is constructed from aplurality of flexible metallic strips of relatively flat rectangularcross-section. By virtue of the structural relationship of the strips inthe completed structure, relatively light weight strips such asreferring to the simplified schematic showing of FIGS. '1 and 2. FIG. 1is an approximate plan view of the interrelationship of a simplifiedframe structure embodying the invention when the structure is expandedinto To point out the relationship of the strips, it is convenient tomake reference to an imaginary base circle B and an imaginary apexcircle A. The base circle and apex circle are both centered upon avertically extending axis of symmetry. In the schematic view of FIG. 1,twelve symmetrically spaced base locations 13 through 12B are indicated.For the sake of clarity, those strips having their lower ends located atbase locations 3B, 6B, 9B and 1213 have been indicated in heavy line,the remaining strips being shown in relatively light lines. In thesimplified schematic cross-sectional view of FIG. 2, the strips shown inlight line in FIG. 1 have been omitted entirely.

At each of base locations 3B, 6B, 9B and 12B a pair of like strips arepivotally interconnected at their lower ends to form a strip pair. Thepair of strips having their lower ends pivotally interconnected at baselocation 12B are identified as 12-1 and 12-2. It is convenient todescribe the strip pair as comprising a first strip 12-1 which extendsupwardly from base location 12B to an upper end located at apex location3A. Strip 12-1 not only extends upwardly from base location 12B but alsoextends circumferentially about the vertical axis of symmetry in agenerally clockwise direction. The other strip of the strip pair, strip12-2, extends upwardly from base location 12B to apex location 9A. Thesecond strip, 12-2 of the strip pair under consideration extendscircumferentially about the vertical axis in an opposite sense from thedirection of inclination of strip 12-1.

Corresponding nomenclature has been applied to the various stripsextending from base locations 3B, 6B and 9B. In each case the firststrip which is inclined in a clockwise circumferential direction asviewed in FIG. 1 has been designated by the subscript 1, the secondstrip of the strip pair being designated. by the subscript 2.-

All strips are of equal length and each strip extends from a location onthe base circle to a location on the apex circle.

Strips 6 1 and 6-2 are pivotally connected at. their lower ends at baselocation 6B which is diametrically opposedfrom base location 1213. Strip6-1 ispivotally interconnected at location 9A to the upper end of strip12-2, while strip 62 is pivotally connected at its upper end to theupper end of strip 12-1 at apex location 3A. The pivotallyinterconnectcd strips 12-1, 1 2 -2, 6-1'and 6-2 define a unit of thecomplete frame structure. Each strip of the unit extends along a greatcircle arcof the hemispherical dome defined by the expanded framestructure, and each unit may be said to define the'boundary of aspherical lune.

Strips 3-1, 3-2 and 9-1 and 9-2 are pivotally interconnected in asimilar fashion to define a second unit which, as best seen in FIG. 1,extends transversely of the structure with respect to the unit extendingbetween locations 6B and 1213. At each point of. intersection betweenthe strips of different units, the strips are pivotally interconnectedto each other as at 20, 22, 24 and 26.

It is believed apparent that the strips having their lower ends locatedat the remaining base locations are pivotally interconnected in asimilar fashion. At each intersection of each strip, the strips arepivotally interconnected. In all cases, the axis of the pivotalinterconnection between strips is oriented so that a projection of theaxis in the expanded condition of the frame would pass through thevertical axis of symmetry at the intersection of the axis with thecenter 'of base circle B. In other words, the axes of pivotalinterconnections all extend radially of the hemispherical surfacedefined by the expanded frame members.

While the structure schematically represented in FIGS. 1 and 2 shows thebase circle divided into twelve equally spaced base locations, it is'believed apparent that any even number of symmetrically disposed baselocations could be employed, dependent largely upon the size of thecompleted structure.

The specific locations of the points of pivotal intersection between thevarious strips may be determined either geometrically or mathmaticallyfrom their relationships in the expanded position of the structure.

One exemplary form of expansible frame structure embodyingthe inventionis shown in FIGS. 3 through 8. Referring first to FIG. 3, the firststructural embodiment shows a hemispherical dome framework in itsexpanded position, the structure having an imaginary base circle dividedinto twenty-four equally spaced base locations. The embodiment of FIGS.3 through 8 may be compared with the schematic representations of FIGS.1 and 2 by stating that base locations 110B, 120B and 110013, etc.,numbered in sequence corresponding to hour positions on a clock face,correspond respectively to base locations 1B, 2B, and 10B of FIGS. 1 and2. From each of the even numbered base locations in FIG. 3, a strip pairextends upwardly from the base circle to a location on an apex circlecorresponding to the apex circle A of FIGS. Land 2. Thus, as in FIGS. 1and 2, the strip pair projecting upwardly from base location 130B, forexample, is joined at its upper ends to the respective upper ends of thestrip pair projecting upwardly from the diametrically opposed baselocation 190B.

Midway between base locations 110B and 120B, an intermediate baselocation 115B denotes the base location of a strip pair 115-1 and 115-2.Strips 115-1 and 115-2 do not extend completely from the base circle tothe apex circle but terminate at a location somewhat below the apexcircle. Strip 115-1 and strip 1115-2 perhaps illustrate the extent ofthese strips most clearly. Thus, strips 115-1 and strip 1115-2 intersecteach other at a location 28 well below the apex circle, The twostrip arepivotally interconnected at location 28 and are respectively proje cted.beyond their point of intersection to bepivdtally 4 interconnected as at30 and 32 to strips -1 and 1110-2. The strips projecting upwardly fromremaining odd numbered base locations such as B, B, etc. are constructedin identical fashions to strips 115-1 and 1115-2.

To provide a doorway for access to the interior of the completedstructure, certain strips are cut away as indicated at base locations110B and 1125B.

To increase the rigidity of the, expanded structure, a. compressionringassembly. indicated generally at C in FIG. 3 is pivotallyinterconnected with the various strips in a manner best seen in FIGS; 6through 8. As is apparent from FIG. 3, when the structure is in itsexpanded position, compression ring assembly C extends around thecircumference of the structure, in a circular path at a location betweenthe base circle and apex circle of the completed structure. Compressionring assembly C is constructed from a plurality of like links 34 (seeFIG. 6), each link 34 being pivotally connected at a point ofintersection betweenvarious stripssuch as the point 36 at theintersection of strips 110-2 and 120-1'. The pivotal interconnection 36extends through both of the strips and link 34.

The links 34 are pivotally connected to each other at each end in a headto tail relationship by a simple pivotal connection 38 connecting thestrip 34 of FIG. 6v to an adjacent strip 34. As best seen in FIG. 6,strip 34 is notched as at 40,to receive a lug 42 on the end of strip34." An oppositely disposed lug 44 on the opposite end of link 34 isreceived within a complementary notch 46 on the adjacent link. This formof connection prohibits the various links 34 from pivoting beyond theposition shown in FIG. 3 butpermits them to collapse in the fashionshown in FIG. 4 as the. structure is collapsed.

' To further assist the framework in, maintaining its expanded shape, abase line 48 is interconnected between the pointsof pivotalinterconnection of the lower ends of the various steps to prevent thestrips from moving outwardly beyond the imaginary base circle of thecompleted structure.

As can be observed by comparing FIGS. 3, 4 and 5, the structure may becollapsedfrom the hemispherical dome defining expanded position of FIG.3 successively into a substantially paraboloid structure of FIG. 4, anda conical shape structure as. shown in FIG. 5. When fully collapsed, thestructure defines a substantially tubular form.

Referring now to FIGS. 9-11, one exemplary form of structure forinterconnecting the upper ends of the various strips isdisclosed. Thestructure of FIGS. 9-11 serves two purposes-first to assist in expandingor collapsing the frame structure, and second to lock the struc/ tureagainst movement in either direction from its expanded position.

For convenience in description, it will be assumed that the structure ofFIGS. 9-11 is employed upon a six unit frame structure corresponding tothe schematic diagram of FIGS. 1 .and 2. For convenience, a numberingsystem similartothat employedin FIGS. land 2 is employed 9-11 with thereference numerals in FIGS. 9 and :10 being primed.

From the discussion of theschematic diagram of FIG. 1, itwill berecalled thatone unit of the structure consisted of strips 6-1 and 62which were pivotally interconnected to each other at theirlower ends andpivotally connected at their .upper ends respectively to strips 12-2and. 12 -1, strips 12-2 and 12-1being pivotally interconnected to eachother at their lower ends at a base location diametrically opposed fromthe. base location of strip pair 6-1 and 62. Referring now to thecorresponding strips 6-1 62, 12-1, and 12-2 of FIG. 9, it is seenthatthe pivotal interconnection between the upper ends of. strips 6-2and 12-.1 is extended through the respective strips and through anadditional link 230 which extends radially. inwardly from-the pi-votalinterconnection at 3A. Theinnerendof 230 is pivotally connected to a lug231 fixedly secured to a circular plate 200. The pivotal interconnectionbetween link 230 and lug 231 establishes an axis of pivotal movementwhich extends horizontally as opposed to the direction of the pivotalaxis at 3A which, as will be recalled, extends radiaJly of the expandedhemispherical structure.

A similar link 290 extends radially from the pivotal interconnection at9A between strips 6-1 and 122' to a similar lug 291 fixed to plate 200and to which the link 290 is pivotally connected for relative rotationabout a horizontal axis. Similar link and lug connections are providedbetween plate 200 and all twelve pivotal interconnections located on theapex circle, such as link 210 from the pivotal connection at 1A, link220 from the pivotal connection at 2A etc.

A vertically extending shaft 202 is fixed to and extends downwardly fromplate 200. A sleeve 204 is slideably mounted upon shaft 202 and is splitaxially and threaded at its lower end to receive a compression lock-nut206 by means of which sleeve 204 may be clamped to shaft 202 at selectedaxial positions on the shaft. At its upper end, a plurality of radiallyextending lugs such as 208 are fixed to sleeve 204 to provide structurefor pivotally interconnecting a series of links such as 232 to thesleeve. Referring specifically to the link 232, it will be noted thatthe upper end of link 232 is pivotally interconnected to link 230 as at234 while its lower end is pivotally connected to a lug 208 as at 236.Twelve equally spaced radially projecting lugs 208 are secured to sleeve204, each lug providing a pivotal mounting for the lower end of a linkwhich is pivotally interconnected at its upper end to one of the upperlinks corresponding to 210, 220, 230 etc. at the various positions.

It is believed apparent that when the structure is in its expandedposition, see FIGS. 9 and 10, sleeve 204 will be moved to its upperlimit of movement and clamped in position with lock-nut 206. Thecoupling between the shaft and strips by means of the various linksrigidifies the structure at its upper portion. When the structure ispartially expanded, as in the position shown in FIGS. 4 and 11, downwardforces applied to shaft 202 will assist in moving the structure to itsfully expanded position.

lN FIGS. 12-14, a modified form of expanding and locking assembly isdisclosed. As in the case of the embodiment of FIGS. 9l1, a radiallydisposed link extends between each upper pivotal connection betweenstrips inwardly to a common plate upon which the strips are pivotallysecured for rotation about respective horizontal axes. in the PEG. 12-14embodiment, a rigid frame structure 300 is suspended from a centralplate 302 and is coupled to the plate to be capable of rotation about avertical axis with respect to the plate. From the lower end of theframework a plurality of upwardly and outwardly inclined struts 304 ofV-shaped cross-section project in radial directions. The struts arelocated symmetrically about the vertical axis of the framework and, whenthe structure is in the expanded position, each strut is located toengage one of a plurality of links such as 306 at its outer end in thefashion best shown in FIG. 14. Links such as 306 correspond to links210, 220, 230 etc. of FIG. 9, each link 306 being coupled to framestrips in the same fashion as the links of PEG. 9. When the structure isto be collapsed, rigid frame 300 is pulled downwardly to disengage thelinks from the struts and rotated about the vertical axis to locate thestruts out of alignment with the respective links, as in FIG. 12.

The structures described above provide a relatively light expansibleframework which may be easily expanded to form a frame which may becovered with fabric to form a tent or weatherproof enclosure. Theconstruction is such that the framework may be easily collapsed into asubstantially tubular form of relatively small diameter and is thusreadily portable.

While we have disclosed certain illustrative embodiments of ourinvention, it will be apparent to those skilled in the art that thedisclosed embodiments may be modified. Therefore, the foregoingdescription is to be considered exemplary rather than limiting, and thetrue scope of our invention is that defined in the following claims.

We claim:

1. An expansible frame structure shiftable between a contracted positionin which said structure defines an elongate substantially frusto-conicalshape and an expanded position in which said structure defines a hollowsubstantially hemispherical dome-like shape, said structure in either ofsaid positions having a vertical axis of symmetry extending upwardlyfrom the center of a base circle to the center of an apex circle, saidstructure comprising a plurality of elongate flexible first stripshaving their lower ends located at symmetrically spaced locations uponsaid base circle, said first strips being inclined upwardly from saidbase circle to extend circumferentially in a first direction about saidaxis to terminate at their upper ends at symmetrically spaced locationson said apex circle, a plurality of elongate flexible second stripshaving a length equal to the length of said first strips, a first pivotlocated on the lower end of each of said sec- 0nd strips pivotallyconnecting the lower end of the second strip to the lower end of one ofsaid first strips to define a strip pair, the second strip of each strippair being inclined upwardly from said first pivot to extendcircumferentially about said axis in a direction opposite to said firstdirection to terminate upon said apex circle at a location where thefirst and second strips of each strip pair are symmetrically disposedrelative to each other on opposite sides of a vertical plane containingsaid axis and the first pivot of the strip pair, a second pivot on theupper end of each of said second strips pivotally connecting the upperend of the second strip of each strip pair to the upper end of a firststrip of another strip pair, a series of third pivots interconnectingsaid strip pairs to each other at locations intermediate the ends of thestrips, restraining means interconnecting the lower ends of said strippairs to each other to maintain said first pivots on a base circle ofrelatively large maximum radius when said structure is in said expandedposition, and means pivotally interconnecting said strips at a locationabove said base circle operable when said structure is in said expandedposition to flex said strips to extend along great circle arcts of ahemispherical surface of radius substantially equal to said relativelylarge maximum radius and to establish a maximum radius of said apexcircle materially smaller than said relatively large maximum radius.

2. A frame structure as defined in claim 1 wherein said means pivotallyinterconnecting said strips above said base circle comprises acompression ring assembly comprising a plurality of links pivotallyconnected between adjacent strips to extend circumferentially aroundsaid structure along a circle located intermediate said base circle andsaid apex circle when said structure is in said expanded position.

3. A frame structure as defined in claim 1 wherein said means pivotallyinterconnecting said strips above said base circle comprises a shaftextending along said axis, a plurality of link means pivotally connectedat one end to the upper end of said shaft, each of said link means beingpivotally connected at its other end to one of said second pivots, asleeve slideably mounted upon said shaft, a plurality of actuatinglinks, each actuating link being pivotally connected at one end to saidsleeve and at the other end to one of said link means, and means forlocking said sleeve to said shaft to selected locations thereon.

4. A frame structure as defined in claim 1 wherein said means pivotallyinterconnecting said strips above said base circle comprises a plate, aplurality of links, 'each link being pivotally connected at one end tosaid plate and at its opposite end to one of said second pivots, a rigidframe pivotally connected at its upper end to said plate for rotationrelative to said plate about said axis of symmetry, said frame includinga central shaft depending ward-1y projecting fingers rigidly connectedto said shaft,

each'of said fingers being engageable with one of said links to maintainsaid structure in said expanded position.

5. An expansible frame structure shiftable between a contracted positionin which said structure defines an elongate substantially frusto conicalshape and an expanded position in which said structure defines a hollowsubstantially hemispherical dome-like shape, said struc ture in eitherof said positions having a vertical axis of symmetry extending upwardlyfrom the center of a base circle to the center of an apex circle, saidstructure comprising a plurality of elongate flexible first strips ofuniform length having their lower ends located at symmetrically spacedlocations upon said base circle, said first strips being inclinedupwardly from said base circle to extend circumferentially in a firstdirection about said 'axis and terminating at their upper ends atsymmetrically spaced locations on said apex circle, a plurality ofelongate fiexible second strips having a length equal to the length ofsaid first strips, a first pivot located on the lower end of each ofsaid first strips pivotally connecting the lower end of a first strip tothe lower end of a second strip to define a strip pair, the second stripof each strip pair being inclined upwardly from its lower end to extendcircumferentially about said axis in a direction opposite to said firstdirection to terminate upon said apex circle at a location where thefirst and the second strip of each strip pair of symmetrically disposedrelative to each other on opposite sides of a vertical plane containingsaid axis and the first pivot of the strip pair, a second pivot on theupper end of each of said first strips pivotally connecting the upperend of the first strip of each strip pair to the upper end of a secondstrip of a first other strip pair, a third pivot on each first stripspaced a first distance from the upper end of the first strip pivotallyconnecting the first strip of each strip pair to a second strip of asecond other strip pair at a location spaced said first distance fromthe upper end of the second strip, first tension means interconnectingthe lower ends of said strip pairs to each other to maintain the lowerends of said strips on a base circle of relatively large maximum radiuswhen said structure is in said expanded position, and second tensionmeans pivotally interconnecting the upper ends of said strips to eachother to maintain the upper ends of said strips upon an apex circlehaving a maximum radius materially smaller than said relatively largemaximum radius to thereby flex said strips to extend along great circlearcs of a substantially hemispherical surface of radius substantiallyequal to said relatively large maximum radius.

6. A frame structure as defined in claim 5 wherein said second tensionmeans comprises a shaft extending along said axis, a plurality of firstlinks each pivotally connected at one end to the upper end of saidshaft, each of said first links being pivotally connected at itsopposite end to one of said second pivots, a sleeve slideably mountedupon said shaft, and a plurality of second links, each of said secondlinks being pivotally connected at one end to said sleeve and at itsother end to one of said first links whereby axial movement of saidsleeve upon said shaft expands and contracts said apex circle, and meansfor locking said sleeve to said shaft at selected axial positionsthereon.

7. A frame structure as defined in claim 5 wherein said second tensionmeans comprises a plate, a plurality of links each pivotally connectedat one end to said plate, each of said links being pivotally connectedat its other end to one of said second pivots, a rigid frame pivotallyconnected to said plate for movement relative to said plate about saidaxis of symmetry, said frame comprising a shaft depending downwardlyfrom said plate, and a plurality of fingers projecting upwardly andoutwardly from said shaft, each of said fingers being engageable withone of said links to maintain said structure in said expanded position.

References Cited in the file of this patent UNITED STATES PATENTS2,571,634 Von Gunten Oct. 16, 1951 2,865,387 Annibaldi Dec. 23, 1958FOREIGN PATENTS 83,677 Austria Apr. 25, 1921 114,827 Australia Mar. 19,1942

